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The Impressor
Copyright © April 1997 Barber-Colman Company
1260-IN-010-0-03
The Impressor
Hand-Held Portable Hardness Tester
Instruction Manual
1260-IN-010-0-03 Barber-Colman Company, Loves Park, IL
Page 1 of 8

The Impressor
Operation
Recommended Numbers of Reading for Model 934-1
The Impressor is intended for handheld testing of hardness for the following
materials (aluminum and aluminum alloy, soft metals, plastics, fiberglass, rubber
and leather). Harder materials cannot be tested with the Impressor. For
information on the available impressor models, refer to the current revision of the
Barber-Colman Product Guide.
To test a surface, place the indenter point and the leg of the impressor on the same
plane of the surface. Make certain that no indentations from previous use are within
1/16th of an inch of the present indenter point position, to insure reading accuracy.
Readings should not be taken on both sides of the .031-thick test disks. Readings
taken on top of old indentations will adversely affect the accuracy of the reading.
An ample supply of appropriate test discs should be maintained for these reasons.
Press down firmly, but carefully, on the impressor handle. Observe the indicator
reading, noting the peak reading. For softer materials there will be some fallingoff
of the reading from the peak value. This is normal and is due to the nature of
the materials being tested.
As a general rule, the number of readings taken increases with the softness of the
materials being tested. Refer to the table below for recommended minimal
numbers of readings for various materials using the Model GYZJ 934-1. Though
specific numbers for Models GYZJ 935 and GYZJ 936 are not included due to
correlation difficulties with softer materials, the numbers suggested for reinforced
plastics serve as a starting point for softer materials.
GYZJ 934-1
Reading Range
For an Average
Variance of
Recommended
Number of Readings
Homogeneous Material:
80 0.28 3
70 0.28 4
60 0.28 5
50 0.28 6
40 0.28 7
30 0.28 8
20 0.28 9
Reinforced Plastics:
70 0.72 5
60 0.78 10
50 0.75 16
40 0.78 22
30 0.77 29
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Page 2 of 8

The Impressor
Operation (continued)
The indenter point must always be perpendicular to the surface being tested. To
maintain perpendicularity, the leg of the Impressor must be on the same plane as
the indenter point, with both flats of the leg touching the same surface. Irregularlyshaped
objects to be tested should be mounted in a holding jig to assure that
perpendicularity is maintained. For flat objects, a temporary offset of the leg to
accommodate the thickness of the part being tested can be obtained by placement
of washer(s) of appropriate thickness between the leg and the case of the
impressor. Without perpendicularity, accuracy of the reading cannot be assured.
Maintenance
The Impressor is a precision mechanical instrument and should always be handled
with care. The deflection indicator built-in to the Impressor has a normal reading
of zero when not in use.
The Indenter Point has a tip precisely-machined to very small dimensions and
should be used with care to prevent damaging it. Avoid sliding or scraping the
Indenter Point when it is in contact with the surface being tested. If the Indenter
Point becomes damaged, it must be replaced with a new one. The Impressor ships
with two spare Indenter Points.
WARNING
Do not attempt to regrind an Indenter Point when damaged! The mechanical
dimensions of the Indenter Point determine the accuracy of readings
and will create erroneous reading when reground.
To check the condition of the indenter point, first visually inspect it for damage.
Then place the impressor on a hard, flat surface with the appropriate test disc
positioned under the indenter point. Press the impressor handle down firmly, but
carefully, to avoid sideways slippage of the indenter point. The reading on the
indicator should be within the range of values stamped on the test disc. If it is not,
refer to the calibration procedure below.
Replacing the Indenter Point
1. Remove the two screws that hold the impressor case halves together (see
Figure 1).
2. Lift out the frame while holding the spring sleeve in place (so it will not fall off)
until it can be removed.
3. Loosen the plunger upper guide nut with the provided wrench until the crossnotched
top lip protrudes above the frame.
4. Hold the impressor upside down (so the spring and plunger won’t fall out), then
loosen the lock nut with the provided wrench and remove the lower plunger guide.
5. Replace the indenter point in the lower plunger guide, then re-install the lower
plunger guide, leaving about 3/16 of an inch of thread protruding below the frame.
6. Gently press the indenter point against a hard surface such as glass until the
indicator shows a maximum reading. Care should be taken not to damage the
indicator by forcing it beyond its full deflection of about 110 Barcol units on the dial.
Tighten or loosen the lower plunger guide until a reading of 100 is obtained.
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Page 3 of 8

The Impressor
Maintenance (continued)
7. Tighten the lock nut, then re-check the maximum deflection as in step 6 above.
8. Tighten the plunger upper guide nut until its top is flush with the frame.
9. Calibrate the impressor per the procedure below.
10. Replace the spring sleeve, reassemble the case halves and screws, and test
for the appropriate reading on the test discs.
Calibration Procedure
Test the hardness of the appropriate test disc specified below. If the reading is
higher than the larger value stamped on the test disc, tighten the plunger upper
guide nut further into the frame. Test again. If the reading is lower than the smaller
value stamped on the test disc, loosen the plunger upper guide nut. Test again.
If reading within the specified limits cannot be obtained by plunger upper guide nut
adjustment only, loosen the lock nut and make minor adjustments to the lower
plunger guide. Retighten the lock nut and test again. Repeat until readings are
between the values stamped on both test discs.
Test Discs for the Model 934-1
Use the GYZJ 250 test disc stamped 87/89 for the model GYZJ 934-1 in step 9
above. Then repeat the procedure in step 9 using the GYZJ 78 test disc labelled
43-48. Iterate between these test discs until the optimum reading for both discs
is obtained. This procedure will provide the optimum accuracy over the entire
range of the 934-1. If optimized readings cannot be obtained on both test discs,
this indicates that the indenter point may be damaged. Replacement of the
indenter point is recommended.
The above procedure can also be used between any two reference materials with
known Barcol values at the extremes of a portion of the impressor reading range.
Calibration at these known values will provide enhanced accuracy within that
portion of the range, but not outside of that range.
Test Disc for the Model 935
Use the GYZJ 69 test disc stamped 87-89 for the Model GYZJ 935 in step 9 above.
Test Disc for the Model 936
Use the GYZJ 70 test disc stamped 48-50 for the model GYZJ 936 in step 9 above.
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Page 4 of 8

The Impressor
Specifications
Note:
Physical characteristics of very soft materials are such that uniform correlation
between different hardness measuring systems cannot be established. For this
reason, conversion curves should be considered tentative. We recommend that
impressor hardness limits for each material be established by test.
Typical Readings of Aluminum Alloys
Alloy and Temper: 1100-0 3003-0 3003H14 2024-0 5052-0 5052H14 6061T6 2024T3
GYZJ 934-1 reading: 35 42 56 60 62 75 80 85
Approximate Conversion Curves
for GYZJ 934-1
140
130
120
110
Rockwell "B" (1/16" ball 100 kg load)
Rockwell "E" (1/8" ball 100 kg load)
Rockwell "F" (1/16" ball 60 kg load)
Brinnell (10 mm ball 500 kg load)
Vickers Pyramid Numbers
Brinnell
Vickers
Rockwell "H"
Rockwell-Brinell-Vickers Numbers
100
90
80
70
60
50
40
Rockwell "E"
Rockwell "B"
Rockwell "F"
30
20
Webster
10
Approximate Conversion Curves
for GYZJ 935 & GYZJ 936
90
0
35
40 50 60 70 80 90 100
Barber-Colman Impressor Number
80
70
GYZJ-936
Type D Durameter
60
50
40
30
GYZJ-935
20
10
0
50 60 70 80 90
Impressor Dial Indication
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Page 5 of 8

The Impressor
Operating Information (continued)
Approximate Conversion Chart for GYZJ 934-1
GYZJ- Brinell Vickers Webster Rockwell
934-1 10mm 500kg 5kg Model B B E F H
35 21 32
36 22 35
37 23 37
38 24 40
39 25 42
40 25 26 45
41 25 27 47
42 26 28 49
43 27 29 51
44 27 30 54
45 28 30 56
46 29 31 58
47 30 32 23 60
48 30 33 0.7 26 62
49 31 34 1.3 28 64
50 32 35 1.9 31 66
51 33 36 2.5 34 68
52 34 38 3.1 36 70
53 35 39 3.6 39 30 72
54 37 40 4.2 41 34 73
55 38 41 4.7 44 37 75
56 39 43 5.3 46 40 77
57 40 44 5.8 48 43 78
58 42 45 6.3 50 46 80
59 43 47 6.8 53 48 82
60 45 49 7.3 55 51 83
61 46 50 7.8 57 54 85
62 48 52 8.3 59 56 86
63 50 54 8.8 61 59 88
64 51 56 9.2 63 61 89
65 53 58 9.7 65 63 90
66 55 60 10.1 67 66 92
67 57 62 10.6 69 68 93
68 60 65 11.0 71 70 94
69 62 67 11.4 73 72 95
70 64 70 11.8 17 75 74 97
71 67 72 12.2 23 76 75 98
72 69 75 12.6 28 78 77 99
73 72 78 12.9 33 80 79 100
74 75 81 13.3 38 81 80 101
75 78 85 13.7 42 83 82 102
76 80 88 14.0 47 84 83 103
77 84 92 14.3 51 86 85 104
78 87 95 14.7 55 87 86 105
79 90 99 15.0 59 89 88 106
80 94 103 15.3 63 90 89 106
81 97 108 15.6 66 91 90 107
82 101 112 15.9 70 92 91 108
83 105 117 16.2 73 94 92 109
84 109 121 16.4 76 95 93 109
85 113 126 16.7 79 96 94 110
86 117 131 16.9 81 97 95 111
87 121 137 17.2 84 98 96 111
88 126 142 17.4 86 99 97 112
89 130 17.6 88 100 98 112
90 135 17.8 90 101 98 113
91 140 18.0 102 99 114
92 145 18.2 103 100
93 18.4 103 100
94 18.6 104 101
95 18.7 105 102
96 18.9 106 102
97 19.0 106 103
98 19.2 107
99 19.3 107
100 19.4 108
Appoximate Conversion Chart for
GYZJ-935 and GYZJ-936
Type D
Durameter
GYZJ-
935
GYZJ-
936
52
6
53
9
54
12
55
15
56
18
57
21
58
24
59
27
60
30
61
32
62
35
63
38
64
40
65
43
66
45
67
48
68
22
50
69
26
52
70
30
54
71
34
57
72
38
59
73
41
61
74
45
63
75
48
65
76
51
67
77
54
69
78
57
70
79
60
72
80
63
74
81
66
76
82
69
77
83
71
79
84
74
80
85
76
82
86
79
83
87
81
85
88
83
86
89
85
87
90
87
88
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Page 6 of 8

The Impressor
Repair Parts
Contact factory (RPPL) for repair parts prices
Figure 1. Impressor Cutaway
Item GYZJ-934-1 GYZJ-935 GYZJ-936 Description Qty
1 AYRS-62 AYRS-62 AYRS-62 Spring 1
2 BYRF-3114 BYRF-3114 BYRF-3114 Cover Screw 2
3 BYRF-250 BYRF-250 BYRF-250 Frame Screw 1
4 GYZJ-2 GYZJ-2 GYZJ-2 Plunger Upper Guide Nut 1
5 GYZJ-3 AYRS-146-1 AYRS-146-1 Spring† 1
6 GYZJ-4-1 GYZJ-4-1 GYZJ-4-1 Plunger 1
7 GYZJ-6-5 GYZJ-6-5 GYZJ-67 Indenter Point† 1
8 GYZJ-7 GYZJ-7 GYZJ-7 Lever 1
9 GYZJ-8 GYZJ-8 GYZJ-8 Pin 1
10 DYRA-218 DYRA-218 DYRA-218 Pin 1
11 GYZJ-15-2 GYZJ-15-2 GYZJ-15-2 Indicator (not field servicable) 1
12 GYZJ-16 GYZJ-16 GYZJ-16 Lock Nut 1
- GYZJ-17-1 GYZJ-17-1 GYZJ-17-1 Wrench 1
- GYZJ-19-2 GYZJ-19-2 GYZJ-19-2 Carrying Case 1
13 GYZJ-23-1 GYZJ-23-1 GYZJ-23-1 Case & Frame Assembly 1
14 GYZJ-61 GYZJ-61 GYZJ-61 Stop Ring 1
15 GYZJ-62 GYZJ-62 GYZJ-62 Point Sleeve 1
16 GYZJ-63 GYZJ-63 GYZJ-63 Spring Sleeve 1
17 GYZJ-64 GYZJ-64 GYZJ-71 Lower Plunger Guide† 1
18 GYZJ-65 GYZJ-65 GYZJ-65 Leg 1
19 GYZJ-79-1 GYZJ-79-2 GYZJ-79-3 Label†
† Parts required to convert between models.
Hardness Tester
Model
GYZJ-934-1
GYZJ-935
GYZJ-936
Range
25 to 50 Brinell (10 mm ball 500 kg load)
For softer plastic and very soft metals
For extremely soft material
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Page 7 of 8

The Impressor
Certified Test Disks
Part No. Use with Model Barber-Colman Scale
GYZJ-069-100 Set of 5 GYZJ-935 87 – 89
GYZJ-070-100 Set of 5 GYZJ-936 48 – 50
GYZJ-078-100 Set of 5 GYZJ-934-1 43 – 48
GYZJ-250-100 Set of 5 GYZJ-934-1 87/89
Standard Test Disks GYZJ-069 Each GYZJ-935 87 – 89
GYZJ-070 Each GYZJ-936 48 – 50
GYZJ-078 Each GYZJ-934-1 43 – 48
GYZJ-250 Each GYZJ-934-1 87/89
3 Barber-Colman Company, Loves Park, IL
Page 8 of 8